The present invention relates to fluid delivery systems, and in particular to systems and methods for accurately delivering a target volume of fluid to a destination.
Such systems regulate the rate of flow of fluid through a line. Some examples of fluid delivery systems are peritoneal dialysis machines and intravenous fluid delivery systems. These systems may include a permanent housing which does not come into direct contact with the transporting fluid and into which a fluid-exposed disposable cassette is placed. The disposable cassette includes flexible membranes, or other structures that respond to pressure and that separate the permanent components from the fluid being delivered. Examples of such fluid delivery systems and their sub-components (e.g., pressure conduction chambers, flow measurement systems and valves) are disclosed in U.S. Pat. Nos. 4,778,451, 4,826,482, 4,976,162, 5,088,515, 5,178,182 issued to Kamen, U.S. Pat. No. 5,989,423 issued to Kamen et al. and U.S. Pat. No. 6,503,062 issued to Gray et al. These patents are all hereby incorporated herein by reference.
One problem with respect to fluid delivery systems, such as in peritoneal dialysis, arises when treating subjects with low fill volume capacities, such as a child. For example, in peritoneal dialysis systems, a fill volume of 1000 mL or less generally indicates a low fill volume while fill volumes of greater than 1000 mL are typical for an average adult's fill volume. Thus, a single fluid delivery system may not be appropriate for treating both an average adult and a child.
Another problem arises with respect to fluid delivery systems when two or more fluids from two or more sources must be delivered to a subject or patient simultaneously and in a particular ratio. It is difficult to maintain a consistent ratio of the different fluids for simultaneous delivery to the subject because each source may deliver its solution to the system at different rates and/or in different volumes. Consequently, it is difficult to maintain a consistent ratio of the different fluids in the fluid delivery system at any one time.